Theory predicts that in markets with increasing returns, the number of differentiated products and resulting consumer satisfaction grow in market size. We document this phenomenon across 246 US radio markets. By a mechanism that we term 'preference externalities', an increase in the size of the...

Free entry into markets with decreasing average costs and differentiated products can result in an inefficient number of firms and suboptimal product variety. Because new firms and products draw their customers in part from existing products, concentration can affect incentives to enter as well...

In theory, free entry can lead to social inefficiency. When new products are substitutes for existing products, the business stolen from incumbents places a wedge between private and social benefits of entry. The business stealing effect can be offset if entry reduces prices or increases...